The present invention relates to an apparatus for controlling the lighting of a fluorescent lamp for use in a refrigerator and a method therefor, and more particularly, to a fluorescent lamp lighting control apparatus and method for repeating the lighting operation until the fluorescent lamp is illuminated to secure the lighting.
Lamps which are lit according to opening of a refrigerator door are typically installed in a refrigerator. The lamps used in the refrigerator are chiefly incandescent lamps. The reason why an incandescent lamp is used in the refrigerator is due to a faster lighting time than that of a fluorescent lamp. A pre-heating time of approximately one second is generally necessary for lighting a fluorescent lamp. Since a flickering phenomenon occurs in the fluorescent lamp until it is illuminated, fluorescent lamps are used in places where frequent light-up operations are not performed. Hence, it is generally known that it is not preferable to employ a fluorescent lamp in a refrigerator which is frequently opened and closed.
There has been a recent trend toward the use a large-sized refrigerators in which fluorescent lamps are used. Fluorescent lamps have a higher power consumption efficiency in the order of one-third through a quarter times that of incandescent lamps. Also, the fluorescent lamps have the advantage of providing a comfortable light, a small amount of radiation heat and a lifetime of five to ten times that of one incandescent lamp. Therefore, it is appropriate to employ a fluorescent lamp in a large-sized refrigerator.
First, a light-up procedure of a typical fluorescent lamp will be described with reference to FIG. 2 which shows a schematic circuit diagram of a prior art fluorescent lamp light-up circuit. There are a variety of components necessary for lighting a fluorescent lamp 40. Here, a light-up circuit using a starter 35 will be described. Filaments 37 and 38 exists in both inner ends of the fluorescent lamp 40. These filaments 37 and 38 are connected to respective ends of the starter 35. Also, the two filament 37 and 38 are connected to a circuit composed of a stabilizer and an alternating-current (AC) power source 31 both of which are connected in series. As a result, a closed circuit (hereinafter called a preheating closed circuit) is formed by a cycle of the AC power source 31, the stabilizer 33, the left-hand filament 37, the starter 35, and the right-hand filament 38.
A microcomputer 50 detects opening of a refrigerator door and drives a relay 44 to turn on a switch SW, thereby starting the AC power supply 31. When a supply of power from the AC power source 31 starts, power is supplied along the preheating closed circuit to preheat the filaments 37 and 38. Upon the completion of the pre-heating step, a bimetal (not shown) in the starter 35 is cut off and a current flow toward the starter 35 is instantly stopped, to thereby generate a high-voltage counter-electromotive force in the stabilizer 33, cause discharge between the two filaments 37 and 38 in the fluorescent lamp 40 and light up the fluorescent lamp 40. After lighting up the fluorescent lamp 40, another closed circuit (hereinafter called a light-up closed circuit) is formed by a cycle of the AC power source 31, the stabilizer 33, the left-hand filament 37, and the right-hand filament 38, to maintain the lit state of the fluorescent lamp 40. Thereafter, when the refrigerator door is closed, the microcomputer 50 detects the closure of the door, drives the relay 44 to turn off the switch SW and to cut off the power supply from the AC power source 31. Thereby, the fluorescent lamp 40 is put out.
As described above, to light up a fluorescent lamp, a preheating operation and a counter-electromotive force supply from a stabilizer are required. Since the internal chamber in the refrigerator differs from a room in temperature and humidity, optimal preheating time necessary for lighting the fluorescent lamp in the internal chamber and a room is different from each other, to thereby cause an inferior light-up. The fluorescent lamp should be lighted after a time elapse necessary for preheating it, and it is not desirable to excessively preheat the fluorescent lamp to secure the light-up operation because such an excessive preheating may shorten the lifetime of the fluorescent lamp. If a lighting operation is set to a predetermined optimal preheating time, an inferior lighting will probably occur due to change of circumstance of the interior of the refrigerator. By the way, the conventional fluorescent lamp lighting control method maintains the fluorescent lamp in a turned-off state when an inferior lighting occurs. In this case, since the refrigerator door plays a role of a switch which connects and disconnects the power to and from the fluorescent lamp, users must close and open again in order to light up the fluorescent lamp to thereby feel inconvenient.